The present invention relates to a programmable electronic computer of the type having a visual display unit which is employed to facilitate communications between the computer and the user.
Computers are known in which, immediately after the introduction of the information to be processed, it can be communicated to the user on the visual display unit, so that it can be checked and corrected. Moreover, the contents of a working memory can be called on to the visual display unit and then modified at discretion, or the recurrence of particular situations in the program, the machine or the operations to be performed can be made clear on the visual display unit for the intervention of the operator.
In these computers it is not generally possible, during the execution of a program, to display visually the characters introduced on the keyboard. In fact, the time of control of the visual display unit by the central unit of the computer is lost for the purposes of processing operations in the course of a program and is so much the greater the more characters the visual display comprises. Therefore, the control of the visual display unit during the execution of a program slows down the execution itself, whereby the valuable speed characteristics of the central unit become ineffective.